Spin-orbit alignment and magnetic activity in the young planetary system AU Mic

Martioli, Eder; Hébrard, G.; Moutou, C.; Donati, J.‐F.; Artigau, Étienne; Cale, Bryson; Cook, Neil J.; Dalal, S.; Delfosse, X.; Forveille, T.; Gaidos, Eric; Plavchan, Peter; Berberian, John; Carmona, A.; Cloutier, Ryan; Doyon, René; Fouqué, P.; Klein, Baptiste; Étangs, A. Lecavelier des; Manset, N.; Morin, J.; Tanner, Angelle; Teske, Johanna; Wang, S.

doi:10.1051/0004-6361/202038695

Cited by 58 publications

(54 citation statements)

References 28 publications

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“…TOI837 joins a number of other young planetary systems reported from TESS, including DSTucAb, HIP67522b, TOI1726, and AUMicb (Newton et al 2019;Addison et al 2020;Hirano et al 2020;Mann et al 2020;Martioli et al 2020;Montet et al 2020;Palle et al 2020;Plavchan et al 2020;Rizzuto et al 2020;Zhou et al 2020). In the space of planet sizes and ages, the top panel of Figure 11 shows that TOI837 is among the youngest transiting planets known.…”

Section: Discussionsupporting

confidence: 55%

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Bouma

Hartman

Brahm

et al. 2020

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We report the discovery of TOI 837b and its validation as a transiting planet. We characterize the system using data from the NASA Transiting Exoplanet Survey Satellite mission, the ESA Gaia mission, ground-based photometry from El Sauce and ASTEP400, and spectroscopy from CHIRON, FEROS, and Veloce. We find that TOI 837 is a T=9.9 mag G0/F9 dwarf in the southern open cluster IC 2602. The star and planet are therefore -+ Unified Astronomy Thesaurus concepts: Exoplanets (498); Transits (1711); Exoplanet evolution (491); Stellar ages (1581); Young star clusters (1833)

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Section: Discussionsupporting

confidence: 55%

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Bouma

Hartman

Brahm

et al. 2020

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“…The AU Mic host is an M1 star with a spatially resolved edge-on debris disk (Kalas et al 2004) and at least one transiting planet, AU Mic b (Plavchan et al 2020). This Neptune-size planet is in a 8.5-d prograde orbit aligned with the stellar rotation axis (Martioli et al 2020;Hirano et al 2020;Palle et al 2020). While Plavchan et al (2020) only reported an upper limit on the mass of AU Mic b, Klein et al (2021) measured 17.1 +4.7 −4.5 M ⊕ thanks to infrared observations secured with the SPIRou spectropolarimeter (Donati et al 2020).…”

Section: Introductionmentioning

confidence: 98%

New constraints on the planetary system around the young active star AU Mic

Martioli

Hébrard

Correia

et al. 2021

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AU Microscopii (AU Mic) is a young, active star whose transiting planet was recently detected. Here, we report our analysis of its TESS light curve, where we modeled the BY Draconis type quasi-periodic rotational modulation by starspots simultaneously to the flaring activity and planetary transits. We measured a flare occurrence rate in AU Mic of 6.35 flares per day for flares with amplitudes in the range of 0.06% < fmax < 1.5% of the star flux. We employed a Bayesian Markov chain Monte Carlo analysis to model the five transits of AU Mic b observed by TESS, improving the constraints on the planetary parameters. The measured planet-to-star effective radius ratio of Rp∕R⋆ = 0.0496 ± 0.0007 implies a physical radius of 4.07 ± 0.17 R⊕ and a planet density of 1.4 ± 0.4 g cm−3, confirming that AU Mic b is a Neptune-size moderately inflated planet. While a single feature possibly due to a second planet was previously reported in the former TESS data, we report the detection of two additional transit-like events in the new TESS observations of July 2020. This represents substantial evidence for a second planet (AU Mic c) in the system. We analyzed its three available transits and obtained an orbital period of 18.859019 ± 0.000016 d and a planetary radius of 3.24 ± 0.16 R⊕, which defines AU Mic c as a warm Neptune-size planet with an expected mass in the range of 2.2 M⊕ < Mc < 25.0 M⊕, estimated from the population of exoplanets of similar sizes. The two planets in the AU Mic system are in near 9:4 mean-motion resonance. We show that this configuration is dynamically stable and should produce transit-timing variations (TTV). Our non-detection of significant TTV in AU Mic b suggests an upper limit for the mass of AU Mic c of <7 M⊕, indicating that this planet is also likely to be inflated. As a young multi-planet system with at least two transiting planets, AU Mic becomes a key system for the study of atmospheres of infant planets and of planet-planet and planet-disk dynamics at the early stages of planetary evolution.

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“…The magnetically active star AU Mic has a projected rotational velocity of v sin i * = 7.5 ± 0.9 km s −1 (Martioli et al 2020). A periodic pattern is observed in the TESS S1 data at a reported period of 4.86 d (Plavchan et al 2020), which is ascribable to the presence of spots combined with stellar rotation.…”

Section: Stellar Rotationmentioning

confidence: 95%

“…The sky-projected spin-orbit angle of AU Mic b has been measured by several authors: λ = −2.96 +10.44 −10.30 (Palle et al 2020); λ = 0 +18 −15 (Martioli et al 2020); λ = −4.7 +6.8 −6.4 (Hirano et al 2020); Notes. Time notation follows the ISO-8601 convention.…”

Section: Introductionmentioning

confidence: 99%

The changing face of AU Mic b: stellar spots, spin-orbit commensurability, and transit timing variations as seen by CHEOPS and TESS

Szabó

Gandolfi

Brandeker

et al. 2021

A&A

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AU Mic is a young planetary system with a resolved debris disc showing signs of planet formation and two transiting warm Neptunes near mean-motion resonances. Here we analyse three transits of AU Mic b observed with the CHaracterising ExOPlanet Satellite (CHEOPS), supplemented with sector 1 and 27 Transiting Exoplanet Survey Satellite (TESS) photometry, and the All-Sky Automated Survey from the ground. The refined orbital period of AU Mic b is 8.462995 ± 0.000003 d, whereas the stellar rotational period is Prot = 4.8367 ± 0.0006 d. The two periods indicate a 7:4 spin–orbit commensurability at a precision of 0.1%. Therefore, all transits are observed in front of one of the four possible stellar central longitudes. This is strongly supported by the observation that the same complex star-spot pattern is seen in the second and third CHEOPS visits that were separated by four orbits (and seven stellar rotations). Using a bootstrap analysis we find that flares and star spots reduce the accuracy of transit parameters by up to 10% in the planet-to-star radius ratio and the accuracy on transit time by 3–4 min. Nevertheless, occulted stellar spot features independently confirm the presence of transit timing variations (TTVs) with an amplitude of at least 4 min. We find that the outer companion, AU Mic c, may cause the observed TTVs.

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Spin-orbit alignment and magnetic activity in the young planetary system AU Mic

Cited by 58 publications

References 28 publications

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

Cluster Difference Imaging Photometric Survey. II. TOI 837: A Young Validated Planet in IC 2602

New constraints on the planetary system around the young active star AU Mic

The changing face of AU Mic b: stellar spots, spin-orbit commensurability, and transit timing variations as seen by CHEOPS and TESS

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